Digital data transmission apparatus and method for multiplexing multiplexing multi-channel video data within active video periods

ABSTRACT

A digital data transmission apparatus and a transmission method thereof in accordance with the present invention includes a reproduction section for reproducing digital data of n (n is an integer of 2 or more) channels from a recording medium, a multiplexing section for dividing one frame in a television signal into n transmission areas on a line-by-line basis, and multiplexing digital data of the n channels reproduced by the reproduction section on the n corresponding transmission areas on the line-by-line basis, and a transmitting section for transmitting data multiplexed by the multiplexing section.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a division of U.S. application Ser. No. 09/230,662filed May 20, 1999 now abandoned, which is a 371 of PCT/JP98/02739 filedJun. 19, 1998.

FIELD OF THE INVENTION

The present invention relates to a digital data transmission apparatusfor multiplexing and transmitting digital data including video data andaudio data, and a transmission method thereof. More particularly, thepresent invention relates to a digital data transmission apparatus formultiplexing and transmitting the digital data in an active video periodof a television signal, and a transmission method thereof.

BACKGROUND ART

At present, there is generally employed the SMPTE-259M standard, i.e.,Serial Digital Interface (below, referred to as “SDI”) standard astransmission method of digital video signals in broadcasting stations ofall the countries in the world. It is known that the SDI standard isprescribed by the SMPTE (Society of Motion Picture and TelevisionEngineers), and provides that digital data including video data andaudio data are converted into serial data to be transmitted.

Referring to FIG. 13, a concrete description will be given to a digitaldata transmission method under the above-described known SDI standard.It is noted that a description will be given to a transmission methodcorresponding to television signals of the NTSC system in the followingdescription.

FIG. 13 is an explanatory diagram showing a configuration of one framein the SDI standard. It is noted that a straight line H of FIG. 13represents a horizontal pixels of a television signal, and each numericvalue on the straight line H represents a pixel number. A straight lineV of the same figure represents a vertical line of a television signal,and each numeric value on the straight line V represents a line number.

As shown in FIG. 13, in the SDI standard, one frame period is dividedinto a horizontal blanking period, and a vertical blanking period, anoptional blanking period and an active video period in each field of afirst field and a second field constituting the one frame.

The horizontal blanking period is prescribed by the section ofhorizontal pixels of which the pixel numbers range from 1440 to 1715.The horizontal blanking period is provided with EAV (End of ActiveVideo) and SAV (Start of Active Video) on its top portion and endportion, respectively. In the horizontal blanking period between the EAVand SAV, ancillary data such as audio data and user data can betransmitted.

In the active video period, video data of 1440 pixels are multiplexed onevery line to be transmitted as the serial data by a predetermined clockfrequency. It is noted that one pixel is comprised of 8 bits or 10 bitsof video data.

The optional blanking period is a period which is included in thevertical blanking period. However, the optional blanking period canarrange and transmit video data in the same manner as in the activevideo period.

The use of the SDI standard enables the transmission of 4:2:2-componenttelevision signals of one channel not through analog transmissionsystem, ensuring the prevention of degradation in the signals.

On the other hand, in the case where the video data obtained fromdigitization of video signals were processed as they were, the videodata were increased in amount of data, so that the video data wererequired very high data rate (transmission rate). Accordingly, when theabove-described video data were recorded on a recording medium such asmagnetic tape, it was impossible to ensure a sufficient recording time.

In contrast, the handling of the video data by performing compressionthereof in such manner that visual image degradation is not recognizedby bit rate reduction has been known as effective technique. Concretely,there is a DV format prescribed by the HD digital VCR Committee (HighDefinition Video Cassette Reorder Committee), and described in“Specifications of Consumer-Use Digital VCRs using 6.3 mm magnetic tape”as the one in which the bit rate reduction of a video signal is appliedto a home digital VTR.

In the DV format, data compression is performed in two modes accordingto television signals by means of bit rate reduction based on DCT(Discrete Cosine Transform). Concretely, in the DV format, a standardtelevision signal is compressed to 25 Mbps data, while a high-definitiontelevision signal is compressed to 50 Mbps data. The compressed videodata are recorded on the magnetic tape with interleaved audio data, VAUXdata which are data ancillary to the video data, AAUX data which aredata ancillary to the audio data, and sub-code data and the like. In thecase where the data compressed in the 25 Mbps mode are recorded on themagnetic tape, the data for one frame are divided into 10 tracks of themagnetic tape to be recorded. Also, in the case where the datacompressed in the 50 Mbps mode are recorded on the magnetic tape, thedata for one frame are divided into 20 tracks of the magnetic tape to berecorded. It is noted that, as for the concrete information theabove-described VAUX data, AAUX data and sub-code data show, it isdescribed in, for example, the technology of “digital recording andreproducing apparatus” disclosed in Japanese Laid-Open PatentPublication No. 7-226022.

When the video data compressed by the bit rate reduction such as the DVformat are transmitted using the above-described SDI standard, in theprior art, the compression of the video data has been required to beonce decompressed back into a base band signal. Because in the SDIstandard, there is prescribed the transmission method of not thecompressed video data but the non-compressed video data which have notbeen compressed. Further, the SDI standard is intended to transmit thevideo data of the one channel, and hence it has no provisions for thetransmission method for transmitting multi-channel video data. For thisreason, for example, transmission of compressed multi-channel video databetween recording and reproducing apparatuses by the use of the SDIstandard has required that a transmission line was provided for everychannel, and further that at least a decoder and an encoder wereprovided at the transmission line on the transmitting side and thereceiving side, respectively.

Examples of a conventional digital data transmission method to overcomethe forgoing problems include the technology of “digital datatransmission method” disclosed in Japanese Laid-Open Patent PublicationNo. Hei 9-46705. The object of the conventional digital datatransmission method is to transmit multi-channel video signalscompressed by, for example, the DV format, utilizing the existingtransmission lines comprised of coaxial cables.

Here, a concrete description will be given to a conventional digitaldata transmission method with reference to FIG. 14.

FIG. 14 is an explanatory diagram showing a method for multiplexing andtransmitting digital data of six channels using the SDI standard in aconventional digital data transmission method.

As shown in FIG. 14, in the conventional digital data transmissionmethod, the active video period is divided into units of 240 pixels(words), so that six transmission areas are formed on the SDI standard.Six channels 1, 2, 3, 4, 5, and 6 are assigned to the six transmissionareas, respectively. In each of the channels 1 through 6, digitalinterface data (below, referred to as “DIF data”) for the one frame arearranged. Specifically, the DIF data are comprised of a plurality of aDIF block, and the DIF data are arranged in the transmission area sothat three DIF blocks are multiplexed on every line. The DIF data arealso comprised of the video data compressed to the 25 Mbps based on theDV format, the interleaved audio data, the VAUX data, the AUUX data andthe sub-code data.

With the conventional digital data transmission method, in the casewhere the data compression is performed in the 25 Mbps mode as shown inthe same figure, it is possible to multiplex the DIF data up to amaximum of the six channels of the channels 1 through 6 and transmitthem on the SDI standard. Also, in the case where the data compressionis performed in the 50 Mbps mode, two transmission areas can be assignedper one channel to multiplex the DIF data and transmit them on the SDIstandard.

The DIF data for the one frame are comprised of a plurality of a DIFsequence. The DIF sequence is a transmission unit defined by the DVformat. In the case of the 25 Mbps mode, one DIF sequence corresponds toone track on the magnetic tape. Also, in the case of the 50 Mbps mode,the one DIF sequence corresponds to two tracks of the magnetic tape.

A concrete description will be given to the transmission order of theDIF blocks constituting the DIF sequence with reference to FIGS. 15 and16.

FIG. 15 is an explanatory diagram showing a concrete example of thetransmission order of DIF blocks in the case of a 25 Mbps mode. FIG. 16is an explanatory diagram showing a concrete example of the transmissionorder of the DIF blocks in the case of a 50 Mbps mode. Each transmissionorder of the DIF blocks shown in FIGS. 15 and 16 is the same one as thatdescribed in the technology of the foregoing Japanese Laid-Open PatentPublication No. Hei 7-26022.

As shown in FIG. 15, in the case of the 25 Mbps mode, the DIF sequencehas a header DIF block H0, sub-code DIF blocks SC0 and SC1, VAUX DIFblocks VA0 to VA2, audio DIF blocks A0 to A8, and video DIF blocks V0 toV134. These DIF blocks are, as shown in the same figure, sequentiallytransmitted in the order of transmission shown by an arrow of thefigure. Each the DIF has 80 bytes of data.

Next, in the case of the 50 Mbps mode, processing is performed by usingthe processing system in the 25 Mbps mode in two-system parallel. Thatis, data of the odd-numbered tracks of 20 tracks corresponding to datafor one frame are processed by the one processing system, while data ofthe even-numbered tracks are processed by the other processing system.Hereinafter, the data corresponding to the odd-numbered tracks aredefined as sub-channel A, while the data corresponding to theeven-numbered tracks are defined as sub-channel B.

Specifically, first, in the data processing of the video signals in the50 Mbps mode, the one frame is divided into two areas. Then, the data ofthe one area are processed as data of the sub-channel A, while the dataof the other area are processed as data of the sub-channel B. Therefore,in the video signals, the bit rate reduction encoding and decodingprocessing are performed independently in each of the sub-channels A andB. Also, in the audio signals, 1 and 3 channels of four channels aredivided into the sub-channel A, while 2 and 4 channels are divided intothe sub-channel B, thus performing processing.

Subsequently, in the case of the 50 Mbps mode, after data processing isperformed between the sub-channels A and B as described above, as shownin FIG. 16, the respective DIF blocks of the sub-channels A and B arearranged alternately, and thus multiplexed, thereby performing asequential transmission by the order of transmission shown by an arrowof the figure.

However, in the foregoing conventional digital data transmission method,as shown in FIG. 14, the DIF blocks of each channel are multiplexed andtransmitted sequentially three by three within one line. Accordingly, inthis conventional digital data transmission method, in the case wheredata of a plurality of channels are transmitted, each data of aplurality of channels is sent out from the transmitting side to thereceiving side of a transmission path with being mutually mixed withinone line. Consequently, in the conventional digital data transmissionmethod, data cannot be processed in the order inputted in the receivingside of the transmission path. This requires, for example, that thereceived data be held until the data for one frame has been input.

Concretely, the case is conceivable where data are transmitted at highspeed from a digital data recording and reproducing apparatus asapplication for transmitting the digital data of a plurality of channelsincluding the video signals subjected to the bit rate reduction througha digital interface. That is, the data is reproduced from the recordingmedium at high speed such as 4 times normal speed. Then, the data offour channels are multiplexed and transmitted on the transmission pathin accordance with the above-described SDI standard and the like. Thisenables a reduction of time required for data transmission down to ¼. Inthis case, with the video signals of the same material, data of fourchronologically consecutive frames are multiplexed and transmitted inthe active video period of the one frame as data of four channels,respectively. However, in the conventional digital data transmissionmethod, the data of the four frames are not arranged in thechronological order on the transmission path. Accordingly, in anapparatus of the receiving side for receiving data transmitted at highspeed such as recording and reproducing apparatus, there has arisen aproblem that data processing cannot be performed in the order inputted.

Further, in a system for transmitting data of a plurality of differentmaterials simultaneously, the use of conventional digital datatransmission method cannot enable the multiplexing and distribution of,for example, a plurality of data reproduced from their respectivedifferent recording and reproducing apparatuses on a digital interface.This is because as shown in FIG. 14; in the conventional digital datatransmission method, the data of each channel are multiplexed within oneline. Further, the data of each channel are arranged over a plurality oflines, and two fields. For this reason, the multiplexing anddistribution of a plurality of data cannot be performed on aline-by-line basis, or on a field-by-field basis using the conventionaldigital data transmission method.

Further, in the conventional digital data transmission method, as shownin FIGS. 15 and 16, the arrangement of data within the channel ischanged in accordance with the data rate of the data to be transmitted.For example, in the case of the above-described 50 Mbps, the data aretransmitted using the same transmission area as that in the case of twochannels in the 25 Mbps mode. However, in the conventional digital datatransmission method, the arrangement of data within the transmissionarea, that is, the method of multiplexing of data has been changedbetween the case of the 50 Mbps mode and the case of two channels in the25 Mbps mode. Consequently, in the conventional digital datatransmission method, an increase in kind of multiplexing has required anincrease in size of a data multiplexing circuits, and switching ofcontrol in accordance with the contents of data to be handled.Especially, in the apparatus on the receiving side, it has been verydifficult to change data distribution process according to the contentsof the received data and the data rate in real time.

BRIEF SUMMARY OF THE INVENTION

Briefly the present invention is a digital data transmission apparatusfor multiplexing and transmitting compressed digital video data of nchannels within active video periods of one frame of a television signalwhere n is an integer of 2 or more. The digital data transmissionapparatus comprises: a reproduction means for reproducing the digitalvideo data of said n channels from a recording medium; a multiplexingmeans for:(1) dividing said active video periods of one frame of thetelevision signal into n transmission areas, each of the n transmissionareas comprising m consecutive lines, m being a positive integer, (2)packetizing the reproduced compressed digital video data of each of then channels into a plurality of packets having a packet header includinga packet ID, and (3) arranging the packets of the reproduced compresseddigital video data of each of said n channels within one of said ntransmission areas wherein said m consecutive lines comprise thecompressed digital video data of one and only one of said n channels;and a transmitting means for transmitting the packets arranged by saidmultiplexing means within each of the n transmission areas, seriallyfrom a top line to a bottom line of each of the transmission areas.

Another aspect of the present invention comprises a digital datatransmission method for multiplexing and transmitting compressed digitalvideo data of n channels within an active video period of one frame of atelevision signal, where n is an integer of 2 or more, the digital datatransmission method comprising the steps of: dividing said active videoperiod of one frame of the television signal into n transmission areas,each of then transmission areas comprising m consecutive lines, m beinga positive integer, of said one frame of the television signal;assembling the compressed digital video data of each of the n channelsinto a plurality of packets, each of the packets having a packet headerincluding a packet ID; arranging the packets of the compressed digitalvideo data of each of said n channels within one of said n transmissionareas wherein said m consecutive lines comprise the compressed digitalvideo data of one and only one of said n channels; and transmitting thepackets arranged within each of then transmission areas serially from atop line to a bottom line of each of the transmission areas.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing a configuration of a digital datatransmission apparatus in a first embodiment of the present invention.

FIG. 2 is a timing chart showing the operation of multiplexing DIF dataon a channel-by-channel basis in a multiplexer shown in FIG. 1.

FIG. 3 is an explanatory diagram showing a configuration of a DIF packetgenerated by a DIF encoder shown in FIG. 1.

FIG. 4 is an explanatory diagram showing a method for arranging DIFpackets of four channels in an active video period of one frameprescribed in the SDI standard in the digital data transmissionapparatus shown in FIG. 1.

FIG. 5 is a block diagram showing a configuration of a digital datatransmission apparatus in a second embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a method for arranging the DIFpackets of four channels in the active video period of one frameprescribed in the SDI standard in the digital data transmissionapparatus shown in FIG. 5.

FIG. 7 is a block diagram showing a configuration of a digital datatransmission apparatus in a third embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a method for arranging the DIFpackets of two different compressed SDI data in the active video periodof one frame prescribed in the SDI standard in the digital datatransmission apparatus shown in FIG. 7.

FIG. 9 is a block diagram showing a configuration of a digital datatransmission apparatus in a fourth embodiment of the present invention.

FIG. 10 is a timing chart showing the operation of multiplexing the DIFdata on a sub-channel-by-sub-channel basis in a multiplexer shown inFIG. 9.

FIG. 11 is an explanatory diagram showing a method for arranging the DIFpackets of two sub-channels in the active video period of one frameprescribed in the SDI standard in the digital data transmissionapparatus shown in FIG. 9.

FIG. 12 is an explanatory diagram showing a method for arranging the DIFpackets of different data rates in the active video period of one frameprescribed in the SDI standard in the digital data transmissionapparatus shown in FIG. 9.

FIG. 13 is an explanatory diagram showing a configuration of one framein the SDI standard.

FIG. 14 is an explanatory diagram showing a method for multiplexing andtransmitting digital data of 6 channels using the SDI standard in aconventional digital data transmission method.

FIG. 15 is an explanatory diagram showing a concrete example of thetransmission order of DIF blocks in the case of a 25 Mbps mode.

FIG. 16 is an explanatory diagram showing a concrete example of thetransmission order of the DIF blocks in the case of a 50 Mbps mode.

It will be recognized that some or all of the Figures are schematicrepresentations for purposes of illustration and do not necessarilydepict the actual relative sizes or locations of the elements shown.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, preferred embodiments of a digital data transmissionapparatus and a transmission method thereof in accordance with thepresent invention will be described with reference to the accompanyingdrawings.

<<First Embodiment>>

FIG. 1 is a block diagram showing a configuration of a digital datatransmission apparatus in a first embodiment of the present invention.It is noted that, in the following description, a digital datatransmission apparatus for transmitting data at high speed such as 4times normal speed will be described in order to facilitate thecomparison with conventional examples. Further, in the followingdescription, the configuration will be described in which datareproduced at 4 times normal speed are converted to the above-describedDIF data, and multiplexed and output in an active video period of oneframe on the SDI standard. Moreover, it is assumed that the data arecompressed by a data rate of 25 Mbps on a frame-by-frame basis based onthe DV format, and recorded on a magnetic tape. Also, a description willnow be given to the case where the data are read in parallel from themagnetic tape using four heads, and the feed speed of the magnetic tapeis set to be four times that at the time of normal reproduction, therebyto conduct data reproduction at the 4 times normal speed.

As shown in FIG. 1, the digital transmission apparatus of thisembodiment includes a memory 1 for rearranging serial reproduced data51, 52, 53, and 54 simultaneously reproduced from a magnetic tape 100 byfour heads not shown into data on the frame-by-frame basis, and a memorycontroller 2 for controlling the memory 1. Further, the digital datatransmission apparatus of this embodiment includes reproduced dataprocessors 3, 4, 5, and 6 for performing demodulation processingreproduced data 55, 56, 57, and 58 which have been input from the memory1, and rearranged on the frame-by-frame basis respectively, and errorcorrection decoders 7, 8, 9, and 10 connected to the respectivereproduced data processors 3 to 6 and for performing the errorcorrection decoding processing of the input reproduced data,respectively. The error correction decoders 7 to 10 perform the errorcorrection decoding processing of the reproduced data input from therespective reproduced data processors 3 to 6 based on each parity addedat the time of recording, respectively. Then, the error correctiondecoders 7 to 10 output DIF data 59, 60, 61, and 62 each includingcompressed video data, audio data, VAUX data, AAUX data, and sub-codedata, respectively.

In the digital data transmission apparatus of this embodiment, theaforementioned memory 1, memory controller 2, reproduced data processors3 to 6, and error correction decoders 7 to 10 configure a reproductionmeans for reproducing digital data of n (n is an integer of 2 or more)channels from a recording medium.

Further, the digital data transmission apparatus of this embodimentincludes memories 11, 12, 13, and 14 connected to the respective errorcorrection decoders 7 to 10, a memory controller 15 for controlling thememories 11 to 14, and a multiplexer 16 connected to the memories 11 to14. The memories 11 to 14 write and hold the respective DIF data 59 to62 based on a write control signal 63 from the memory controller 15.Also, the memories 11 to 14 read the respective holding DIF data 59 to62 based on read control signals 64, 65, 66, and 67 from the memorycontroller 15, and output them to the multiplexer 16, respectively.Thereby, the DIF data 59 to 62 undergo shift of their time axis in thetransmission order from one another, and are output as multiplexed DIFdata 68 from the multiplexer 16 (a detail description thereon is below).

The digital data transmission apparatus of this embodiment is providedwith a DIF encoder 17 connected to the multiplexer 16, and a memory 18connected to the DIF encoder 17. The DIF encoder 17 performspacketizing, insertion of ID, arrangement of DIF packets into apredetermined line, and the like for outputting the multiplexed DIF data68 into a digital interface. The arrangement of the DIF packets isperformed on a line-by-line basis in four transmission areas provided inthe memory 18 (a detail description thereon is below).

The aforementioned memories 11 to 14, memory controller 15, multiplexer16, DIF encoder 17, and memory 18 configure a multiplexing means fordividing one frame of a television signal into n transmission areas onthe line-by-line basis, and multiplexing digital data of n channelsreproduced by the reproduction means on the n corresponding transmissionareas on the line-by-line basis.

Further, the DIF encoder 17 is successively connected to a driver 19constituting a transmission means, and an output terminal 20. The driver19 subjects the DIF packets input from the DIF encoder 17 to coding(channel coding) for data transmission, and outputs them to the outputterminal 20. The output terminal 20 is connected to a transmission path(not shown) such as coaxial cable, and the multiplexed data aresequentially transmitted therethrough.

In the below, a concrete description will now be given to the operationof the digital data transmission apparatus of this embodiment withreference to FIG. 1. It is noted that a description is omitted on theprocessing of VAUX data, AAUX data, and sub-code data multiplexed on theDIF data 68.

First, the reproduced data 51 to 54 are read in parallel from themagnetic tape 100 by the four heads, and once written in the memory 1.Each of the reproduced data 51 to 54 is data for one frame, andreproduced from the magnetic tape 100 with being divided into units ofits track. As a result of this, in the memory 1, rearrangementprocessing into the data on the frame-by-frame basis is performed withthe control of the memory controller 2.

Next, the reproduced data 55 to 58 are read in parallel from the memory1 to the reproduced data processors 3 to 6, respectively. Each of thereproduced data 55 to 58 is data on the frame-by-frame basis. Also, theorder of the reproduced data 55 to 58 on a time axis is, assuming that kis a natural number, the k, (k+1), (k+2), and (k+3) th frames,respectively.

Then, in the reproduced data processors 3 to 6, the demodulationprocessing of the respective reproduced data 55 to 58 is performed,individually. Thereafter, the reproduced data processors 3 to 6 outputthe demodulated data to the error correction decoders 7 to 10 eachconnected thereto, respectively. Subsequently, in the error correctiondecoders 7 to 10, the respective input data are individually subjectedto the error correction decoding processing based on each parity forerror correction added at the time of recording, and written in thememories 11 to 14 as the DIF data 59 to 62, respectively.

Next, in the memories 11 to 14 and the multiplexer 16, themultiplex-processing is performed for multiplexing the DIF data 59 to 62of four channels input in parallel on one processing system on thechannel-by-channel basis.

A concrete description will be given to the multiplex-processing of theDIF data 59 to 62 with reference to FIG. 2. It is noted that, in thefollowing description, the systems for performing processing with thememories 11, 12, 13 and 14, respectively, are defined as channel 1,channel 2, channel 3, and channel 4, in this order.

FIG. 2 is a timing chart showing the operation of multiplexing DIF dataon a channel-by-channel basis in a multiplexer shown in FIG. 1.

In FIG. 2, the DIF data 59 to 62 for one frame are written into thecorresponding memories 11 to 14, respectively, at the same timing basedon the write control signal 63 (FIG. 1) from the memory controller 15(FIG. 1). The DIF data 59 to 62 are required to be multiplexed on thetime axis from the channel 1 in order at the time of reading. For thisreason, the memory controller 15 first reads the DIF data 59 for oneframe of the channel 1 from the memory 1. Thereafter, the memorycontroller 15 reads the DIF data 60 to 62 for one frame from thememories 12 to 14 in the order of channel 2, channel 3, and channel 4,respectively. Accordingly, the memory controller 15 outputs the writecontrol signal 63 with respect to all of the memories 11 to 14 at thesame timing. On the other hand, the memory controller 15 outputs readcontrol signals 64 to 67 (FIG. 1) for the memories 11 to 14 inaccordance with their corresponding read-out positions of the DIF data59 to 62 of the respective channels 1 to 4, respectively.

In the multiplexer 16, the DIF data 59 to 62 each for one framesequentially read from the respective memories 11 to 14 are multiplexedon a time axis for each of the channels 1 to 4, to be output as the DIFdata 68. It is noted that, the multiplex-processing is time axiscompression processing for performing compression on a time axis withrespect to the DIF data 59 to 62 of the respective channels 1 to 4.Accordingly, the read operation from the memories 11 to 14 is performedat 4 times the frequency of the write operation.

The DIF data 68 multiplexed by the multiplexer 16 is input in the DIFencoder 17 (FIG. 1). The DIF encoder 17 packetizes the input DIF data68, and adds a packet header which is identifying information, a parityfor error correction and the like thereto. Further, the DIF encoder 17arranges the DIF packets of the respective channels 1 to 4 inpredetermined lines on the SDI standard for four transmission areasprovided in the memory 18 (FIG. 1).

A concrete description will now be given to the configuration of the DIFpacket generated by the DIF encoder 17 with reference to FIG. 3.

FIG. 3 is an explanatory diagram showing a configuration of a DIF packetgenerated by a DIF encoder shown in FIG. 1.

As shown in FIG. 3, the DIF packet which is a packet for transmittingthe DIF data 68 is comprised of a packet header 200, two DIF blocks 201and 202, and a parity for error correction 203 (in the figure,abbreviated as “ECC”). Each of the DIF blocks 201 and 202 has 80 wordsof data amount, and is a block of the minimum unit which configures themultiplexed DIF data 68 from the multiplexer 16 (FIG. 1). The DIFencoder 17 adds the packet header 200 comprised of 7 words, and theparity for error correction 203 comprised of 4 words to the twogenerated DIF blocks 201 and 202. This generates one DIF packet. Afterbeing packetized by the DIF encoder 17 (FIG. 1) in this manner, the DIFpacket is multiplexed in the predetermined line in the active videoperiod of one frame on the SDI standard. Subsequently, coding for datatransmission is performed by the driver 19 (FIG. 1). Then, the data inwhich the DIF packets are multiplex on the SDI standard are output fromthe output terminal 20 (FIG. 1) to the outside. In the followingdescription, the data in which digital data including video datacompressed on the SDI standard is referred to as Compressed SDI data.

It is noted that, in the aforementioned description, the configurationwas described whereby the DIF encoder 17 performs the packetizingprocessing for generating the DIF packet. However, the configuration canbe properly adopted whereby packetizing is performed using the memories11 to 14 for multiplexing, and the packet header 200 and parity forerror correction 203 are added in the DIF encoder 17.

A concrete description will now be given to a transmission method forarranging and transmitting DIF packets for four channels in the activevideo period of one frame on the SDI standard with reference to FIG. 4.

FIG. 4 is an explanatory diagram showing a method for arranging DIFpackets of four channels in an active video period of one frameprescribed in the SDI standard in the digital data transmissionapparatus shown in FIG. 1.

As shown in FIG. 4, the one frame in the television signal prescribed inthe SDI standard is divided into the four transmission areascorresponding to the respective four channels 1 to 4 on the line-by-linebasis. That is, a predetermined number of lines, for example, 94 linesare assigned to each transmission area of the channels 1 to 4.

Concretely, as shown in the same figure, the DIF packets of the channel1 are arranged between the 21st line and the 114th line, and thusmultiplexed. Similarly, the DIF packets of the channel 2, the DIFpackets of the channel 3, and the DIF packets of the channel 4 arearranged between the 115th line and 208th line, between the 284th lineand the 377th line, and between the 378th line and the 471st line,respectively, and thus multiplexed.

The number of DIF packets of each of the channels 1 to 4 is 750 packetsper frame. That is, the DIF data for one frame is generated into 750 DIFpackets by the DIF encoder 17 (FIG. 1). These DIF packets aremultiplexed in groups of 8 packets on the line-by-line basis, andsequentially transmitted on the predetermined line-by-line basis. Thearrangement of these DIF packets is performed by writing data into thefour transmission areas set in the memory 18 (FIG. 1) corresponding tothe respective channels 1 to 4. Thus, the DIF packets of the respectivechannels 1 to 4 undergo time-division multiplexing on the line-by-linebasis, and transmitted in the same order as that recorded in themagnetic tape. Therefore, even in the case where the compressed SDI dataoutput from the digital data transmission apparatus of this embodimentare received at an apparatus on the receiving side of the transmissionpath such as server apparatus, and the compressed SDI data are recordedin hard disk and the like, it becomes possible to perform sequentialrecording in hard disk in the order received. Consequently, in thedigital data transmission apparatus of this embodiment, processing suchas rearranging of data is not required as in the conventional exampledescribed with reference to FIG. 14, which also eliminates the need fora memory and the like for the rearrangement processing.

It is noted that the lines for multiplexing the DIF packets of therespective channels 1 to 4 are not limited to the ones shown in FIG. 4,but can be freely set in accordance with applications. For example, theconfiguration can be properly adopted in which the channels 2 and 4 aremultiplexed with several lines being interposed after the channels 1 and3, respectively.

As described above, in the digital data transmission apparatus of thisembodiment, when the data of a plurality of channels are comprised ofdata of consecutive frames of the same sequence, the data of eachchannel can be multiplexed on the line-by-line basis in chronologicalorder reproduced, and transmitted.

It is noted that, in the digital data transmission apparatus of thisembodiment, a case where high-speed transmission is performed at the 4times normal speed is taken as illustration. However, it is possible tofurther increase the number of channels, thereby performing muchhigher-speed transmission.

<<Second Embodiment>>

FIG. 5 is a block diagram showing a configuration of a digital datatransmission apparatus in a second embodiment of the present invention.In this embodiment, in a configuration of the digital data transmissionapparatus, the configuration is adopted in which data of four differentmaterials are converted into compressed SDI data, thereby to betransmitted. The other elements and portions are similar to those of thefirst embodiment, and therefore superposed descriptions on the similarpoints are omitted.

As shown in FIG. 5, in the digital data transmission apparatus of thisembodiment, the reproduced data processors 3 to 6 are connected to fourhard disks 101, 102, 103, and 104, respectively. The hard disks 101 to104 record data 69, 70, 71, and 72 of mutually different sequences 1, 2,3, and 4, respectively. The hard disks 101 to 104 simultaneouslyreproduce data 69 to 72, and output them to the reproduced dataprocessors 3 to 6, respectively.

The reproduced data processors 3 to 6 perform the demodulationprocessing of data for the respective input data 69 to 72, and outputthem to the error correction decoders 7 to 10, respectively. Each of theerror correction decoders 7 to 10 performs the error correction decodingprocessing of input data based on the parity for error correction addedat the time of recording in the same manner as in the first embodiment.Thereafter, the error correction decoders 7 to 10 output theabove-described sequences 1 to 4 as DIF data 73, 74, 75, and 76 of therespective channels 1 to 4 to memories 11 to 14, respectively. It isnoted that, in the digital data transmission apparatus of thisembodiment, the above-described reproduction means is comprised of thereproduced data processors 3 to 6, and the error correction decoders 7to 10.

The subsequent processing is the same as that described in the firstembodiment. The DIF data 73 to 76 are multiplexed on the time axis inone processing system for each of the channels 1 to 4, and output as DIFdata 77 from the multiplexer 16 to the DIF encoder 17. Thereafter, theyare converted to packets by the DIF encoder 17, and then multiplexed inthe active video period of one frame of the SDI standard usingtransmission areas in the memory 18. Then, they are output as thecompressed SDI data through the driver 19 from the output terminal 20 tothe outside.

A concrete description will now be given to the transmission method withthe digital data transmission apparatus of this embodiment withreference to FIG. 6.

FIG. 6 is an explanatory diagram showing a method for arranging the DIFpackets of four channels in the active video period of one frameprescribed in the SDI standard in the digital data transmissionapparatus shown in FIG. 5.

In the transmission method of the first embodiment shown in FIG. 4,there have been arranged DIF packets of four consecutive frames of thesame sequence in the active video period of one frame. In contrast, inthe transmission method of this-embodiment, as shown in FIG. 6, thereare arranged DIF packets of four channels of different sequences 1 to 4.However, the arrangement of the DIF packets in each of the channels 1 to4 is entirely the same as that in the first embodiment shown in FIG. 4.Thus, the DIF packets of the respective channels 1 to 4 are arranged onthe line-by-line basis in the transmission areas in the memory 18 (FIG.5), and transmitted. Therefore, in the digital data transmissionapparatus of this embodiment, even in the case where data of differentsequences are transmitted simultaneously in multi-channel, they can bemultiplexed and distributed as the DIF data of each channel on thefield-by-field basis and on the line-by-line basis.

<<Third Embodiment>>

FIG. 7 is a block diagram showing a configuration of a digital datatransmission apparatus in a third embodiment of the present invention.In this embodiment, in the configuration of the digital datatransmission apparatus, the configuration is adopted in which compressedSDI data from a plurality of reproducing devices are multiplexed andtransmitted. The other elements and portions are similar to those of thefirst embodiment, and therefore superposed descriptions on the similarpoints are omitted.

As shown in FIG. 7, the digital data transmission apparatus of thisembodiment includes two reproducing devices 21 and 22, and a multiplexer23 connected to the reproducing devices 21 and 22. The reproducingdevices 21 and 22 reproduce compressed SDI data 78 and 79, and outputthem to the multiplexer 23, respectively. The multiplexer 23 selects theinput compressed SDI data 78 and 79 based on the control from theoutside control device (not shown), and outputs them to the outside ascompressed SDI data 80 of one channel.

A concrete description will now be given to a transmission method withthe digital data transmission apparatus of this embodiment withreference to FIG. 8.

FIG. 8 is an explanatory diagram showing a method for arranging the DIFpackets of two different compressed SDI data in the active video periodof one frame prescribed in the SDI standard in the digital datatransmission apparatus shown in FIG. 7.

As shown in FIG. 8, in the active video period of the first field, thereare arranged and multiplexed DIF packets obtained by dividing thecompressed SDI data 78 from the reproducing device 21 into units ofpacket. The multiplexer 23 selects and outputs these DIF packets as thecompressed SDI data 80 of the channels 1 and 2. Also, in the activevideo period of the second field, there are arranged and multiplexed DIFpackets obtained by dividing the compressed SDI data 79 from thereproducing device 22 into units of packet. The multiplexer 23 selectsand outputs these DIF packets as the compressed SDI data 80 of thechannels 3 and 4.

As described above, in the digital data transmission apparatus of thisembodiment, the compressed SDI data from different reproducing devicesand the DIF packets of the compressed SDI data are arranged andmultiplexed on the channel-by-channel basis and on the line-by-linebasis, respectively. With this configuration, in the digital datatransmission apparatus of this embodiment, it becomes possible tomultiplex and assign digital data onto the transmission path on theline-by-line basis and on the field-by-field basis. Further, in the casewhere only a predetermined channel of a plurality of channels isreceived by an apparatus on the receiving side, it is possible toextract the compressed SDI data of the required channel by specify thelines to be received.

<<Fourth Embodiment>>

FIG. 9 is a block diagram showing a configuration of a digital datatransmission apparatus in a fourth embodiment of the present invention.In this embodiment, in the configuration of the digital datatransmission apparatus, such the configuration is adopted that in whichcompressed SDI data is transmitted corresponding to two different datarates. The other elements and portions are similar to those of the firstembodiment, and therefore superposed descriptions on the similar pointsare omitted. It is noted that, in the following description, the twodata rates of 25 Mbps and 50 Mbps prescribed in the DV format are usedto give a description for facilitating the comparison with theconventional example described with reference to FIGS. 15 and 16. Also,it is assumed that the 25 Mbps which is the same data rate as that ineach of the foregoing embodiments is a first data rate, while the 50Mbps which is the data rate twice thereof is a second data rate.

As shown in FIG. 9, the digital data transmission apparatus of thisembodiment includes the reproduced data processors 3 and 4 forperforming demodulation processing of reproduced data 81 and 82simultaneously reproduced from the magnetic tape 100 by two heads (notshown), respectively, and the error correction decoders 7 and 8individually connected to the respective reproduced data processors 3and 4 and for performing the error correction decoding processing of theinput reproduced data. The error correction decoders 7 and 8, in thesame manner as those in the first embodiment, perform the errorcorrection decoding processing of the reproduced data input from thereproduced data processors 3 and 4 based on the corresponding paritiesadded at the time of recording, respectively, and output DIF data 83 and84 each including compressed video data, audio data, and sub-code datato the memories 11 and 12, respectively. It is noted that, in thedigital data transmission apparatus of this embodiment, theabove-described reproduction means is comprised of the reproduced dataprocessors 3 and 4, and the error correction decoders 7 and 8.

In the digital data transmission apparatus of this embodiment, thememories 11 and 12 and the multiplexer 16 output DIF data 85 obtained bymultiplexing the DIF data 83 and 84 of the respective two sub-channels Aand B in parallel input from the respective error correction decoders 7and 8 onto one processing system to the DIF encoder 17.

Below, a concrete description will now be given to the operation of thedigital data transmission apparatus of this embodiment with reference toFIG. 9.

First, the reproduced data 81 and 82 are read in parallel from themagnetic tape 100 by the two heads, and output to the reproduced dataprocessors 3 and 4, respectively.

Next, in the reproduced data processors 3 and 4, there is individuallyperformed the demodulation processing of the respective reproduced data81 and 82. Thereafter, the reproduced data processors 3 and 4 output thedemodulated data to the respective error correction decoders 7 and 8respectively connected thereto. Subsequently, in the error correctiondecoders 7 and 8, the error correction decoding processing of the inputdata are performed based on each parity for error correction added atthe time of recording, and written as DIF data 83 and 84 to the memories11 and 12, respectively.

Next, in the memories 11 and 12 and the multiplexer 16, there isperformed a multiplex-processing for multiplexing the DIF data 83 and 84of the two respective sub-channels A and B input in parallel onto oneprocessing system.

A concrete description will now be given to the multiplex-processing ofthe DIF data 83 and 84 with reference to FIG. 10.

FIG. 10 is a timing chart showing the operation of multiplexing the DIFdata on a sub-channel-by-sub-channel basis in the multiplexer shown inFIG. 9.

In FIG. 10, the DIF data 83 and 84 each for one frame are written intothe corresponding memories 11 and 12 at the same timing based on thewrite control signal 63 (FIG. 9) from the memory controller 15 (FIG. 9),respectively. The DIF data 83 and 84 are required to be multiplexed onthe time axis in the order of sub-channels A and B at the time ofreading. Therefore, the memory controller 15 first reads the DIF data 83for one frame of the sub-channel A from the memory 11, and then readsthe DIF data 84 for one frame of the sub-channel B from the memory 12.Accordingly, the memory controller 15 outputs the write control signal63 with respect to the memories 11 and 12 at the same timing. On theother hand, the memory controller 15 outputs read control signals 64 and65 (FIG. 9) for the memories 11 and 12 in accordance with each read-outposition of the DIF data 83 and 84 of the respective sub-channels A andB, respectively.

In the multiplexer 16, the DIF data 83 and 84 each for one framesequentially read from the respective memories 11 and 12 are multiplexedfor each of the sub-channels A and B on the time axis, to be output asDIF data 85 of one system. It is noted that, the multiplex-processing istime axis compression processing for performing compression on the timeaxis with respect to the DIF data 83 and 84 of the respectivesub-channels A and B. Accordingly, the read operation from the memories11 and 12 is performed at frequency quadruple that of the writeoperation.

The subsequent processing is the same as those described in the firstand second embodiments. The DIF data 85 multiplexed onto one processingsystem is output from the multiplexer 16 to the DIF encoder 17 (FIG. 9).Thereafter, they are converted into packets by the DIF encoder 17, andmultiplexed in the active video period of one frame of the SDI standardusing transmission areas in the memory 18 (FIG. 9). Then, they areoutput as the compressed SDI data through the driver 19 (FIG. 9) fromthe output terminal 20 (FIG. 9) to the outside.

A concrete description will now be given to the transmission method withthe digital data transmission apparatus of this embodiment withreference to FIG. 11.

FIG. 11 is an explanatory diagram showing a method for arranging the DIFpackets of two sub-channels in the active video period of one frameprescribed in the SDI standard in the digital data transmissionapparatus shown in FIG. 9.

As shown in FIG. 11, in each of the sub-channels A and B, the number ofDIF packets thereof is 750 packets per frame in the same manner as ineach of the aforementioned embodiment. Also, in the case of the 50 Mbpsmode which is the second data rate, the number of DIF packets is 1500packets per frame.

These DIF packets are arranged in groups of 8 packets on theline-by-line basis in the same manner as in other embodiments. For thisreason, the DIF packets of the sub-channel A are multiplexed between the21st line and the 114th line, while the DIF packets of the sub-channel Bare multiplexed between the 115th line and the 208th line, thus to betransmitted, respectively. That is, the DIF packets of the respectivesub-channels A and B are multiplexed on the time axis on asub-channel-by-sub-channel basis, and on the line-by-line basis, to betransmitted as the compressed SDI data 85.

A comparison will now be given between the arrangement of DIF packets inthe sub-channels shown in FIG. 11 and the arrangement of DIF packets inthe channels in each of the first and second embodiments shown in FIGS.4 and 6, respectively. Apparent from the comparison results, DIF packetsare arranged in entirely the same lines between the sub-channel A andthe channel 1, and between the sub-channel B and the channel 2. In otherwords, in the digital data transmission apparatus of this embodiment, inthe case where the data to be transmitted are in the 50 Mbps mode, itbecomes possible to process the data by dividing them into twosub-channels A and B corresponding to one channel in the case of the 25Mbps mode. This enables commonality of multiplexing into compressed SDIdata, and packetizing processing between the 50 Mbps mode and the 25Mbps mode.

Therefore, for example, as shown in FIG. 12, it can be performed easilythat data of one channel of the 50 Mbps mode are multiplexed in thetransmission area of the first field, while data of two channels of the25 Mbps mode are multiplexed in the transmission area of the secondfield.

As described above, in the digital data transmission apparatus of thisembodiment, even in the case where digital data to be transmitted havedifferent data rates such as the 50 Mbps mode and the 25 Mbps mode, theDIF packets in the transmission area are multiplexed on the line-by-linebasis with the same arrangement. Consequently, in the digital datatransmission apparatus of this embodiment, data transmission can beperformed without expanding the circuit size of the multiplexer. Thiscan facilitate the data processing in an apparatus on the receiving sideof the transmission path.

It is noted that, in the aforementioned first to fourth embodiments, adescription has been given to the digital data transmission apparatushandling data compressed by the DV format. However, the DV format is notan exclusive example, and hence data compressed by other bit ratereduction techniques can be properly adopted. For example, the datacompressed based on the MPEG (Moving Picture Experts Group) standard canalso be transmitted in the same manner.

Although the present invention has been described in terms of thepresently preferred embodiments, it is to be understood that suchdisclosure is not to be interpreted as limiting. Various alterations andmodifications will no doubt become apparent to those skilled in the artto which the present invention pertains, after having read the abovedisclosure. Accordingly, it is intended that the appended claims beinterpreted as covering all alterations and modifications as fall withinthe true spirit and scope of the invention.

Industrial Applicability

The present invention is applicable to a digital data transmissionapparatus for multiplexing and transmitting digital data including videosignal and audio signal, and the transmission method thereof. It is usedparticularly for a digital data transmission apparatus for multiplexingand transmitting digital data in the active video period of thetelevision signal, and the transmission method thereof.

1. A digital data transmission apparatus for multiplexing andtransmitting compressed digital video data of n channels, within activevideo periods of one frame of a television signal, n being an integer of2 or more, said digital data transmission apparatus comprising: areproduction means for reproducing the digital video data of saidchannels from a recording medium, a multiplexing means for: (1) dividingsaid active video periods of one frame of the television signal into ntransmission areas, each of the n transmission areas comprising mconsecutive lines, m being a positive integer, (2) packetizing thereproduced compressed digital video data of each of the n channels intoa plurality of packets, each of the packets having a packet headerincluding a packet ID and a length of 1/k times the length of one of them consecutive lines, k being an integer of 2 or more, and (3) arrangingthe packets of the reproduced compressed digital video data of each ofsaid n channels within one of said n transmission areas wherein said mconsecutive lines comprise the compressed digital video data of one andonly one of said n channels, and a transmitting means for transmittingthe packets arranged by said multiplexing means within each of the ntransmission areas, serially from a top line to a bottom line of each ofthe transmission areas.
 2. A digital data transmission apparatusaccording to claim 1, wherein the compressed digital video data of eachof said n channels is chronologically consecutive data of one sequence.3. A digital data transmission apparatus according to claim 1, whereinthe compressed digital video data of each of said n channels is data ofa different sequence from one another.
 4. A digital data transmissionapparatus according to claim 1, wherein said compressed digital videodata are compressed to about a 25 Mbps data rate on a frame-by-framebasis.
 5. A digital data transmission method for multiplexing andtransmitting compressed digital video data of n channels, n being aninteger of 2 or more, within an active video period of one frame of atelevision signal, said digital data transmission method comprising thesteps of: dividing said active video period of one frame of thetelevision signal into n transmission areas, each of the n transmissionareas comprising m consecutive lines, m being a positive integer, ofsaid one frame of the television signal, assembling the compresseddigital video data of each of the n channels into a plurality ofpackets, each of the packets having a packet header including a packetID and a length of 1/k times the length of one of the m consecutivelines, k being an integer of 2 or more, arranging the packets of thecompressed digital video data of each of said n channels within one ofsaid a transmission areas wherein said m consecutive lines comprise thecompressed digital video data of one and only one of said n channels,and transmitting the packets arranged within each of the n transmissionareas serially from a top line to a bottom line of each of thetransmission areas.
 6. A digital data transmission method according toclaim 5, wherein the compressed digital video data of each of said nchannels is chronologically consecutive data of one sequence.
 7. Adigital data transmission method according to claim 5, wherein thecompressed digital video data of each of said n channels is data of adifferent sequence from one another.
 8. A digital data transmissionmethod according to claim 5, wherein said compressed digital video dataare compressed to about a 25 Mbps data rate on a frame-by-frame basis.